The goal of this program is to provide physicians-in-training at St. Jude Children's Research Hospital with in- depth laboratory experiences such that they can successfully pursue careers as physician-investigators in the field of hematology/oncology. Applicants to this program will perform laboratory research with preceptors selected from a faculty of experienced investigators in interrelated disciplines relevant to cancer, including: hematology/oncology, molecular pharmacology, biochemistry, immunology, experimental hematology, pharmaceutical sciences, developmental neurobiology, genetics, pathology, and tumor cell biology. Each preceptor is supported by extramural grants, has well-equipped laboratory space, and access to specialized Cancer Center Support Grant-supported shared resource laboratories that provide the latest technology for research in cellular and molecular biology. The program will enroll highly qualified MD's or MD/PhD's who have completed a residency in pediatrics or medicine and desire fellowship training in the subspecialty of hematology/oncology. Funds are requested to support two to three years of basic laboratory research training for each trainee;a year of clinical training mandated by subspecialty boards is funded separately using institutional resources. Trainees will be selected by an Advisory Committee which will evaluate the candidate's credentials and commitment to a career in academic medicine. In addition to the focused laboratory experience, their training will include exposure to often neglected aspects of cancer research: biostatistics;scientific writing;the design, conduct, and interpretation of clinical trials;and ethical issues related to biomedical research. Further training opportunities will be provided through both institutional and departmental workshops, seminars, retreats, poster sessions, and journal clubs. The trainees will meet regularly with the program director, the training grant Advisory Committee, and the preceptor, so that evaluation and advisement is on-going. Serious concerns abound nationwide about a relative paucity of well-trained physician-investigators who can perform independent laboratory research or interact effectively with laboratory investigators so that laboratory discoveries can more effectively be brought to fruition in clinical settings. This manpower concern is particularly acute in Pediatric subspecialties. Graduates of the training program supported by this application will fill this critical need.